Process and device for purifying polluted air

Abstract

A chemisorption filter is provided for receiving contaminated air to be filtered and partially heating the air while filtering same, with a further heater downstream of the chemisorption filter for further heating the air. A catalyst mass is traversed by the air heated by the heater and disposed downstream of the heater for further purifying the air, with further device downstream of the catalyst mass for cooling the air upon passage thereof through the catalyst mass, all of the devices collectively forming an air purifier to a passenger compartment of an automobile for supplying the compartment with purified air. A sensor is provided behind the radiator of the automobile and contacted by the air displaced therethrough by a fan, the sensor detecting contaminant levels in the external air before it is admitted to the chemisorption filter, for controlling the on/off operation of the air purifier.

We claim: 
     
       1. A filter system for the removal of contaminants from air to be delivered to an automotive vehicle passenger compartment, comprising, in combination with the radiator of the vehicle through which air is displaced by a fan driven by the vehicle engine: means forming a chemisorption filter receiving contaminated air to be filtered and partially heating said air while filtering same;   heating means downstream of said chemisorption filter for further heating said air;   means containing a catalyst mass traversed by the air heated by said heating means and disposed downstream of said heating means for further purifying the air;   means downstream of said catalyst mass for cooling the air upon passage thereof through said catalyst mass, all of said means collectively forming an air purifier connected to said comparment for supplying said compartment with purified air; and   a sensor located behind said radiator and contacted by the air displaced therethrough by said fan for detecting contaminant levels in the external air before it is admitted to said chemisorption filter, for controlling the on/off operation of said air purifier.   
     
     
       2. The filter system defined in claim 1 wherein said sensor is positioned with respect to said radiator and said fan so as to be swept tangentially by the air displaced by said fan. 
     
     
       3. The filter system defined in claim 1, further comprising another sensor responsive to contaminant levels in air admitted to said compartment and located downstream of said air purifier, and a central display connected to said sensors for indicating contaminant levels detected by at least one of said sensors. 
     
     
       4. The filter system defined in claim 1, further comprising control means responsive to said sensor for automatically switching on and off a fan displacing air through said air purifier into said compartment. 
     
     
       5. The filter system defined in claim 1, further comprising control means responsive to said sensor for automatically switching over from the passage of external air into said compartment to the recirculation of air from said compartment to avoid subjecting the compartment to peak levels of contaminants. 
     
     
       6. The filter system defined in claim 1 wherein said sensor is a semiconductor sensor provided in a circuit electrically stabilized for contaminant concentrations of less than 1 ppm. 
     
     
       7. The filter system defined in claim 1 wherein said sensor is provided in a circuit containing a temperature compensating element located directly on said sensor. 
     
     
       8. The filter system defined in claim 1 wherein said temperature compensating element is a heater maintaining said sensor at a constant temperature. 
     
     
       9. The filter system defined in claim 1 wherein said sensor is located in a cowling behind said radiator and ahead of said fan in a forward direction of travel of said vehicle. 
     
     
       10. The filter system defined in claim 9 wherein said sensor is inclined inwardly and rearwardly into said cowling. 
     
     
       11. The filter system defined in claim 3 wherein said other sensor is provided with means for discharging air from said air purifier to the exterior of said vehicle upon detection of a desorption phase of said chemisorption filter. 
     
     
       12. The filter system defined in claim 1, further comprising a resistor connected in parallel to said sensor for linearizing the output thereof. 
     
     
       13. The filter system defined in claim 1, further comprising a PTC resistor with essentially the same temperature coefficient of resistance as said sensor connected in a bridge circuit with said sensor. 
     
     
       14. The filter system defined in claim 13, further comprising an amplifier connected to said bridge circuit, a comparator connected to said amplifier, and an effector circuit connected to said comparator for controlling said air purifier upon the contaminant concentration in said air exceeding a permissible contaminant concentration. 
     
     
       15. The filter system defined in claim 14, further comprising an adjustable voltage divider connected to said comparator for setting a threshold level thereof. 
     
     
       16. The filter system defined in claim 14, further comprising an integrated lowpass filter between said amplifier and said comparator for suppressing signals representing small contaminant peaks. 
     
     
       17. The filter system defined in claim 1, further comprising means for controlled heating of said sensor. 
     
     
       18. The filter system defined in claim 1, further comprising a housing for said sensor, an amplifier connected to said sensor located in said housing, and means for generating a controlled heating voltage for said sensor located in said housing. 
     
     
       19. The filter system defined in claim 18 wherein said housing is perforated in the region of said sensor.